Saturday, December 5, 2009

Week 12 of the regular NFL season is over and with five more weeks to go the playoff picture is starting to take shape. The predictive algorithms we chose are coming along fine. Some are doing better than others which is to be expected.

One of the algorithms we are using leverages Google's PageRank algorithm. We formed a directed graph where each vertex is one of the 32 NFL teams. A directed edge is placed for each game played with the loser pointing to the winner. The edge is then weighted with the margin of victory(mov). The mov is the winner's score - the loser's score.

Then the page rank is calculated using the graph. We are using the igraph library in R to calculate the page rank. The teams are then ranked in order of page rank. This is similar to another group that has used PageRank to rank NFL teams.

One of the concepts of PageRank is that good pages are pointed to by other good pages. In our case good teams will be pointed to by good teams.

An interesting observation that we have made is the difference in rank between the New Orleans Saints and the Indianapolis Colts. After week 12 both teams are undefeated with 11 wins each. However most of the teams that the Colts have beaten were not in the top tier of the league and even when they were the Colts did not beat them by many points.

One example is New England. New England is still a pretty good team this year and they have been beaten by both the Colts and the Saints. The Colts barely won by one point where the Saints beat New England by 21 points.

Here is an animated gif showing the page rank of teams week to week. The edges show which teams played who and the size of the node is a function of the page rank.

Now looking forward to the playoffs we take a look at a still of Week 12.

The Saints are pretty much going to take the NFC and depending on who takes the AFC North we can see the Saints winning the Superbowl over the Bengals.

--Greg Szalkowski

2009-12-9 Edit: The animated GIF from above has been uploaded to YouTube -- MLN.